Samples must be pure and stable. The volume of each sample / buffer is >=100 uL (140-160uL is easier for operation and recommended if having sufficient materials). To correct possible structure factor (influence of inter-particle interaction among molecules under study), three or more concentrations are recommended for each type sample/molecule, e.g., 1, 2, 4 mg/ml. Besides samples, matching buffers are also required for background measurements. To reduce the influence of possible beam drifting, measurements are done in the following order: one buffer, 3-4 samples, one buffer, 3-4 samples, ...